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Overview
Comment:Use __sync_synchronous(), when available, instead of a mutex when a memory barrier is needed.
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SHA1:7d4562e9d577e21406e05300b9a1ad56fded2309
User & Date: drh 2016-07-29 14:23:23
Context
2016-07-29
14:31
Enhance a debugging log message to better identify a mutex. check-in: e60cb6d8 user: dan tags: debug
14:23
Use __sync_synchronous(), when available, instead of a mutex when a memory barrier is needed. check-in: 7d4562e9 user: drh tags: debug
14:10
Add calls to sqlite3_log() when sqlite3_mutex_enter() takes more than 100,000 CPU cycles. check-in: 33c7ef7a user: drh tags: debug
Changes
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Changes to src/os_unix.c.

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** All loads and stores begun before the barrier must complete before
** any load or store begun after the barrier.
*/
static void unixShmBarrier(
  sqlite3_file *fd                /* Database file holding the shared memory */
){
  UNUSED_PARAMETER(fd);



  unixEnterMutex();
  unixLeaveMutex();

}

/*
** Close a connection to shared-memory.  Delete the underlying 
** storage if deleteFlag is true.
**
** If there is no shared memory associated with the connection then this







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** All loads and stores begun before the barrier must complete before
** any load or store begun after the barrier.
*/
static void unixShmBarrier(
  sqlite3_file *fd                /* Database file holding the shared memory */
){
  UNUSED_PARAMETER(fd);
#if defined(__GNUC__) && GCC_VERSION>=4001000
  __sync_synchronize();
#else
  unixEnterMutex();
  unixLeaveMutex();
#endif
}

/*
** Close a connection to shared-memory.  Delete the underlying 
** storage if deleteFlag is true.
**
** If there is no shared memory associated with the connection then this